TL;DR: Two 2025 changes, the IAQM position statement and CSA Group Bulletin PC4, mean an MCERTS certificate is now only as useful as the performance range it actually states. Site managers need to confirm that their monitor was tested at the concentrations and conditions found on their site. Clarity’s Dust Module was independently tested and secured MCERTS certification with an hourly PM10 performance range of 0 to 374 µg/m³, which is well above the UK site action level.

An introduction to Clarity

Clarity Movement has supported air quality monitoring projects worldwide for over 10 years, with more than 10,000 unique deployments across 250+ cities in 85+ countries. Our Sensing-as-a-Service offering provides air quality monitoring hardware, software, and an expert team all in one subscription, with no hidden costs. 

This slide demonstrates the many offerings of Clarity’s Sensing-as-a-Service.

What changed in UK dust monitoring in 2025

UK dust monitoring underwent several changes in 2025. 

The IAQM position statement

In September 2025, the Institute of Air Quality Management (IAQM) published a position statement on using low-cost sensor systems (also known as IAPM, for indicative ambient particulate monitor) for PM10 near demolition and construction sites.

The position statement explained why indicative sensors were not appropriate at the time for monitoring dust (PM10) at elevated concentrations. Most low-cost sensors used at quarries and construction sites underreported PM10 levels. These sensors used an algorithm to estimate PM10 levels based on PM2.5 levels, a method that is less accurate at higher concentrations. Some sensors were not even validated to reach the 190 µg/m³ one-hour UK site action level. 

The position statement provided eight recommendations for dust monitoring. Ideally, the system should measure PM10 directly, be independently validated for the required ranges, and use known sensor algorithms. Relying on MCERTS certification alone is not enough. 

The IAQM also provides additional monitoring guidance.

This webinar slide summarizes the 2025 IAQM Position Statement, including its eight recommendations.

The CSA Group Bulletin PC4

Prior to the position statement, suppliers would give three sensors to be collocated next to a reference site for a period of time. If the data for that certification period fulfilled certain criteria, then the sensor would seemingly be given default sampling ranges on its MCERTS certificates. However, in reality, many of these sensors could not achieve accurate measurements anywhere near the default sampling levels on their certificates. The sensors may not even be calibrated at those levels. 

In July 2025, the CSA Group, which is the body responsible for MCERTS certification, published the MCERTS Product Certification Bulletin PC4. This bulletin removed the default ranges from existing MCERTS certificates. New certified ranges will consist only of what is observed in field testing, such as the observed levels, temperatures, and humidity. 

This webinar slide describes the changes to MCERTS certification as dictated by CSA Group Bulletin PC4. The true ranges for MCERTS-certified sensors were typically up to 75 µg/m³ for PM2.5 and up to 150 µg/m³ for PM10. While these ranges are typical for urban background levels, construction sites can have higher PM10 concentrations. 

Now, there are also two ways that MCERTS is described on the certificates: qualitative MCERTS and quantitative MCERTS. The former is great for tracking trends. It consists of a predefined calibration factor that is determined from the field testing, which you can apply and continue using. 

The latter, quantitative MCERTS, requires collocation of the device and re-checking device calibration at least every 12 months or whenever the device is moved. This requires sensor removal and recolocation over a period of 2 to 4 weeks next to a reference monitor, before reinstallation. 

How we tested the Dust Module for elevated PM10 

Clarity’s products and Dust Module 

Clarity’s flagship product is the Node-S air quality sensor. Measuring fine particulate matter (PM2.5) and nitrogen dioxide (NO2), this sensor is the basic building block of our hardware solution. You can expand the sensing capabilities of the Node-S with Add-On Modules. 

Clarity offers a variety of Add-On Modules for holistic air quality monitoring, as shown in this webinar slide. 

Clarity’s Dust Module is one of these Add-On Modules. It is designed for construction dust and general dust monitoring. It goes beyond the limitations of other low-cost sensors that estimate PM10 from present PM2.5 levels. The Dust Module can measure larger particles directly and detect shifts in particle-size distribution, enabling reliable monitoring in environments with high PM10 levels. It also includes a heated inlet, which minimizes measurement errors from humidity and fog. 

Construction activities often create high dust pollution spikes over shorter periods. The Dust Module’s enhanced sampling frequency lets it capture these shorter spikes, so that no emissions go undetected. Data flows quickly to your Clarity Dashboard and API, without Wi-Fi hotspots or extraneous SIM cards. 

We offer a dashboard specifically designed for construction dust monitoring. If interested, please reach out so we can demo it for you. 

This slide shows Clarity’s Dust Module. The Dust Module attaches seamlessly to our flagship Node-S air quality sensor and uses it for power and connectivity. 

Testing the Dust Module

Before release, we performed a global performance testing campaign across 7 sites and 4 countries. We wanted to avoid cherry-picking good results and instead show consistent performance across a variety of situations. 

This webinar slide shows the Dust Module colocation performance results across 7 sites. The last row, showing median results, demonstrates strong correlation between the reference monitors and the Dust Modules, with a low root mean square error.  

One particularly challenging site where we collocated a Dust Module is Calexico, California. Here, PM10 levels frequently peak above 250 µg/m and particle composition changes over time. The site experiences distinct PM2.5 regimes, driven by both dust and urban sources, including dust storms, agricultural operations, highway traffic, and a parking lot. We tested the Dust Module against FEM instrumentation here from October 10th, 2025, to January 18th, 2026, with Bureau Veritas as the independent test body. Then, we submitted this data set to MCERTS for certification. 

This webinar slide displays the collocation results from Calexico, California, comparing the Dust Module to the BAM reference monitor. On the left is a time-series chart, which has a few gaps from times when the BAM went down. The Dust Module measurements shown in blue overlap well with the reference measurements, shown in black. On the right, the same data is displayed as a scatterplot. The scatterplot shows a strong correlation between the Dust Module measurements and the reference measurements, with R2 = 0.88.

With this collocation data, we secured MCERTS certification with an hourly PM10 performance range of 0 to 374 µg/m³. This is much higher than the UK site action level of 190 µg/m³ and the typical test range for older MCERTS-certified sensors of 150 µg/m³. The Dust Module’s certified range also covers the wide scope of temperatures and relative humidities tested in Calexico. The ambient temperature observed during the test stretched from 8 to 36 degrees Celsius, and relative humidity ranged from 7 to 98% during the test. 

Reading a PC4-era certificate

Before you begin monitoring at your site, there are a few questions you should ask the monitoring equipment supplier to ensure proper air pollution measurement. For instance, you want to understand whether the sensors are co-located at urban background levels or elevated PM10 levels. You want to check whether the stated uncertainty meets the 50% indicative limit required for MCERTS certification and whether the equipment is certified or self-validated. Does the certified range cover your local action level? If it has MCERTS certification, was this certification issued after the PC4 bulletin changes?

This webinar slide lists the questions you should ask your monitoring equipment supplier. These questions are applicable to different kinds of monitoring, not just PM10 measurement.

When reviewing an MCERTS certificate, there are some key points you should look for. If the certificate is up to date, it should have a performance range specified at the bottom. Check that the performance range, site type, and environmental conditions roughly match the environment of your site. Measurement uncertainty should be below 50%, with lower percentages preferred. Ensure that the certificate was issued recently. 

This webinar slide displays the MCERTS certificate issued for the Node-S with the Dust Module. It shows where the certified performance range is on the certificate, along with other key details to look for. To our knowledge, the Dust Module is the first indicative monitor to be certified for elevated dust concentrations. Currently, we are the only ones with a certified performance range on our MCERTS certificate. 

What this means for your sites

Moving forward, a simple MCERTS certification is not enough for your PM10 site monitoring needs. You must actively check that your monitoring equipment has a certified or self-validated range that is ideally above the site action level. 

You may be required to submit the certificate as part of a tender response or local authority check. You may use the certificate as evidence. However, you need to ensure that it includes all required information so the results of your monitoring campaign are not rejected due to an unvalidated sensor or an incorrect certified range. 

Clarity’s Dust Module and Node-S both have the appropriate certified performance ranges for your monitoring needs. They were also tested independently, rather than self-certified. 

This webinar slide clarifies using an MCERTS certificate as evidence. 

Although MCERTS is a UK-focused scheme, it is increasingly requested for worldwide tenders to show independent verification. IAQM guidance sets the template for construction dust methodologies both in the UK and beyond. MCERTS certification is recognized worldwide. 

Looking forward: Dust monitoring with Clarity

To our knowledge, Clarity’s Dust Module is the first indicative monitor to be certified at elevated PM10 levels. Our MCERTS certification is valid until September 2031. The certificate is publicly available on the CSA website, or you can contact us for a copy. Our Dust Module and Suite are available now, and you can contact Lee Swanson, our Account Executive for Europe and Africa, at leeswanson@clarity.io for lead times in your region. 

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